The present invention relates to an antenna unit comprising an antenna and a connection cable, and a computer system having such a unit, particularly to an antenna unit in which an FPC (Flexible Printed Circuit) technology can be suitably used and a computer system having such a unit.
Some conventional computers, for example, notebook PCS (Personal Computers), have a built-in antenna for connection to a network or a peripheral equipment through a wireless LAN or a Bluetooth technique.
FIG. 10 shows a configuration of an example of such a conventional antenna. In an example shown in FIG. 10, an inverted xe2x80x9cFxe2x80x9d antenna 101 has a radio wave resonator 102, a ground 103, and a connection conductor 104 for connecting the radio wave resonator 102 and the ground 103. An antenna unit is constructed by connecting a signal line 106a of a coaxial cable 106 to a feeding point 105 of the radio wave resonator 102, and a shield line 106b of the coaxial cable 106 to the ground 103. In addition, a connector 107 is provided. Usually, the inverted xe2x80x9cFxe2x80x9d antenna 110 is made of several mm thick nickel silver in view of corrosion resistance. Standards IEEE 802.11b (2.45 GHz) and IEEE 802.11a (5.25 GHz) are applied to the wireless LAN, and the frequency of the Bluetooth specification is substantially same as the 2.45 GHz frequency of the IEEE 802.11b specification.
In a communication apparatus as represented by a notebook PC for its requirement to be small and light weight, the apparatus needs to be as compact as possible to minimize the space where the antenna unit is usually mounted. However, in the above described conventional antenna unit, the antenna 101 should have a certain thickness because it is fabricated by stamping from nickel silver, and, the coaxial cable 106 is desired to be as thick as possible to eliminate its signal attenuation, and so a problem arises that an antenna unit cannot be made compact.
In addition, because the frequencies used are as high as several GHz, when the signal line 106a of the coaxial cable 106 is connected to the feeding point 105, for example, by soldering, a problem arises that the positional accuracy for connection should be held high. Thus, even if the position of connection for the signal line 106a to the feeding point 105 is offset from the target position by, for example, 0.1 mm, a resonant frequency is offset by about 10 MHZ.
The present invention is directed to an antenna unit with a radio wave resonator and a connection cable. The antenna unit according to the present invention is integrally formed with the radio wave resonator and the connection cable on a preferably flexible insulating film utilizing preferably FPC techniques.
In the present invention, by forming the radio wave resonator and the connection cable on the flexible insulating film preferably by etching, a thin, flat and flexible antenna unit can be obtained Therefore, when the antenna unit is mounted on an LCD panel which has little free space, it requires little space for mounting because of its flatness, and can be positioned in any location if it is flexible. Further, the radio wave resonator and the connection cable can be formed at one time with high accuracy because the radio wave resonator and the connection cable can be formed by etching which is known as a process to be simple and highly accurate.
In a specific preferred example of the present invention, the connection cable comprises a signal line connected at least to a feeding point of a radio wave resonator, or a signal line connected to the feeding point of said radio wave resonator and two ground circuits provided on both sides of the signal line, and a shield material is provided between said signal line and two ground circuits on one or both of the upper and lower main surfaces of the signal line and the two ground circuits on both sides of the signal line, the shield material being a metal plated, metal powder deposited, or metal foil applied with or without unwoven or woven fabric. Specifically, when the ground circuits and the shield material are provided, a capability for preventing impact of an unnecessary electric wave, the same as for a conventional coaxial cable, can be imparted to a connection cable for the thin and flat antenna unit.
In another specific preferred example of the present invention, the material used for the insulating film is PET (Polyethylene Telephthalate) or PEN (Polyethylene Naphthalate), or LCP (Liquid Crystal Polymer) and the insulating film of PET or PEN is 5-75 mm thick. In any case, both PET and PEN can attain further compactness of the antenna unit inexpensively because they are materials with high dielectric constant and they are inexpensive. In a further specific preferred example, a pair of radio wave resonator and connection cable are formed on the insulating film and the pair of the radio wave resonator and the connection cable are notched to make them bifurcated, the electric component of the radio wave resonator is integrally formed on the insulating film, and the radio wave resonator is of a structure supporting a plurality of frequencies. In any case, the antenna unit can be fully exploited.